Journal:JBIC:17

Peptidylglycine α-Hydroxylating Monooxygenase (PHM)-coordination of peroxide to Cu_M center. Structural and computational study

Katarzyna Rudzka, Diego M. Moreno, Betty Eipper, Richard Mains, Dario A. Estrin and L. Mario Amzel,^[1]

Molecular Tour
In recent years there has been a significant interest in describing the interactions of copper-containing enzymes with O2/H2O2-derived species. The short-lived intermediates resulting from the activation of dioxygen are the key players in the mechanistic cycles in many metalloenzymes. In the enzyme peptidylglycine α-hydroxylating monooxygenase (PHM) various reduced Cu/oxygen species have been proposed to act as catalytically competent intermediates, yet their exact nature and their role in the enzymatic reaction is still unknown. Structural and other studies showed that peptidylglycine α-hydroxylating monooxygenase (PHM) contains two non-equivalent copper sites (CuH and CuM). CuM serves as an oxygen binding and hydrogen abstraction site, CuH is involved in electron transfer. In the structure of Cu(II)-PHM complexed with hydrogen peroxide determined to 1.98 Å resolution, (hydro)peroxide binds exclusively to CuM in a slightly asymmetric side-on mode. The interatomic O-O distance of the copper-bound ligand is 1.5 Å, characteristic of peroxide/hydroperoxide species, and the copper-oxygen distances are 2.0 and 2.1. This Cu(II)-bound peroxo moiety interacts closely with a molecule of water, forming hydrogen bonds that stabilize the structure. DFT and QM/MM calculations indicate that this species is a Cu-bound doubly deprotonated peroxidate and that its energy is similar to that of its isomer Cu(I)-bound superoxide.